1. Field of the Invention
This invention relates generally to devices and methods for collecting and/or detecting biological components in vivo over a period of time. The detection and/or analysis of the biological components collected by the devices may be performed in vivo or ex vivo.
2. Description of the Related Art
Cancer is one of the leading causes of disease, being responsible for 563,700 deaths in the United States each year (Jemal A et al., Cancer statistics, 2004, CA Cancer J Clin. 2004 January-February; 54(1):8-29). For example, breast cancer is the most common form of malignant disease among women in Western countries and, in the United States, is the most common cause of death among women between 40 and 55 years of age (Forrest A P, Screening and breast cancer incidence, J Natl Cancer Inst. 1990 Oct. 3; 82(19):1525-6.). The incidence of breast cancer is increasing, especially in older women, but the cause of this increase is unknown. Malignant melanoma is another form of cancer whose incidence is increasing at a frightening rate, at least sixfold in the United States since 1945, and is the single most deadly of all skin diseases (Jemal et al., 2004).
One of the most devastating aspects of cancer is the propensity of cells from malignant neoplasms to disseminate from their primary site to distant organs and develop into metastases. The early spread of viable tumor cells is considered a hallmark in cancer progression. Despite advances in surgical treatment of primary neoplasms and aggressive therapies, most cancer patients die as a result of metastatic disease. Animal tests indicate that a substantial frequency of circulating cancer cells from solid tumors establish successful metastatic colonies (Fidler, 1993). Studies have found that the detection of circulating metastatic tumor cells and circulating tumor DNA in the blood of cancer patients correlates with cancer progression. (Hoon D S, et al., Molecular markers in blood as surrogate prognostic indicators of melanoma recurrence, Cancer Res. 2000 Apr. 15; 60(8):2253-7, and Taback B, et al., Circulating DNA microsatellites: molecular determinants of response to biochemotherapy in patients with metastatic melanoma, J. Natl. Cancer Inst. 2004 Jan. 21; 96(2): 152-6, herein incorporated in their entirety by reference)
Thus, the detection of occult cancer cells, DNA and tumor markers in the circulation is important in assessing the level of tumor progression and metastasis. Because subclinical metastasis can remain dormant for many years, traditional surveillance measures such as radiological monitoring with CT scans or MRI and nodal biopsy may lack the sensitivity to detect early disease.
Notwithstanding the foregoing, there remains a need for improved methods and devices for detecting biological components of disease.